Apparatus for production of crystal of group III element nitride and process for producing crystal of group III element nitride

ABSTRACT

A manufacturing apparatus of Group III nitride crystals and a method for manufacturing Group III nitride crystals are provided, by which high quality crystals can be manufactured. For instance, crystals are grown using the apparatus of the present invention as follows. A crystal raw material ( 131 ) and gas containing nitrogen are introduced into a reactor vessel ( 120 ), to which heat is applied by a heater ( 110 ), and crystals are grown in an atmosphere of pressure applied thereto. The gas is introduced from a gas supplying device ( 180 ) to the reactor vessel ( 120 ) through a gas inlet of the reactor vessel, and then is exhausted to the inside of a pressure-resistant vessel ( 102 ) through a gas outlet of the reactor vessel. Since the gas is introduced directly to the reactor vessel ( 120 ) without passing through the pressure-resistant vessel ( 102 ), the mixture of impurities attached to the pressure-resistant vessel ( 102 ) and the like into the site of the crystal growth can be prevented. Further, since the gas flows through the reactor vessel ( 120 ), there is no aggregation of an evaporating alkali metal, etc., at the gas inlet or the like, and such an alkali metal does not flow into the gas supplying device ( 180 ). As a result, the quality of Group III nitride crystals obtained can be improved.

TECHNICAL FIELD

The present invention relates to a manufacturing apparatus of Group IIInitride crystals and a method for manufacturing Group III nitridecrystals.

BACKGROUND ART

Group III nitride compound semiconductor such as gallium nitride (GaN)(hereinafter also referred to as a “Group III nitride semiconductor” ora “GaN-based semiconductor”) has been gaining attention as a materialfor semiconductor elements that emit blue or ultraviolet light. A bluelaser diode (LD) is used for high-density optical disk devices ordisplays while a blue light emitting diode (LED) is used for displays,lighting, etc. It is expected to use an ultraviolet LD in the field ofbiotechnology or the like and an ultraviolet LED as an ultravioletsource for a fluorescent lamp.

Generally, Group III nitride semiconductor substrates (for example, GaNsubstrate) that are used for LDs or LEDs are formed by vapor phaseepitaxy. For instance, Group III nitride crystals are grownheteroepitaxially on a sapphire substrate. However, the quality ofcrystals obtained through vapor phase epitaxy has a problem. Morespecifically, crystals obtained by this method generally have adislocation density of 10⁸ cm⁻² to 10⁹ cm⁻² and thus reducingdislocation density has been an important issue. In order to deal withthis issue, efforts have been made to reduce the dislocation density andthereby, for example, an epitaxial lateral overgrowth (ELOG) method hasbeen developed. With this method, the dislocation density can bereduced, but the implementation thereof is complicated, which poses aproblem in practical utilization.

On the other hand, besides the vapor phase epitaxy, a method of carryingout crystal growth from the liquid phase also has been studied. At thebeginning, the liquid phase growth method required super high pressuresand super high temperatures. In this connection, a method has beendeveloped in which crystals are grown in Na flux, thus enabling thealleviation of the pressure and temperature conditions up to about 50atm (50×1.01325×10⁵ Pa) at about 700° C. Recently, single crystals whosemaximum crystal size is about 1.2 mm can be obtained by a method inwhich a mixture of Ga and Na is melted in a nitrogen gas atmospherecontaining ammonia at 800° C. and 50 atm (50×1.01325×10⁵ Pa), and thencrystals are grown for 96 hours using the melt (see, for instance,Patent document 1). Further, a crystal growth apparatus and a growthmethod have been proposed in which pressure is applied to and heat isapplied externally to a reactor vessel (or example, see Patent document2).

FIG. 17 shows one example of the manufacturing apparatus used for aliquid phase growth method (see Patent document 3). As shown in thisdrawing, in this apparatus, a reactor vessel 720 is stored in apressure-resistant vessel 702. Inside the pressure-resistant vessel 702,there is a space surrounded by a heat insulator 711, on an inner wall ofwhich a heater 710 is placed. The reactor vessel 720 is placed in such aspace. A pressure regulator 770 is placed at the top of thepressure-resistant vessel 702. A lid 721 is attached to the reactorvessel 720, and a through hole 724 is formed in this lid 721.

GaN crystals are manufactured using this apparatus, for example, asfollows. First, Ga and N are put in the reactor vessel 720, and thisreactor vessel 720 is stored in the pressure-resistant vessel 702. Then,pressure is applied to the pressure-resistant vessel 702 in a gasatmosphere containing nitrogen while applying heat thereto by the heater710, so that Ga and Na are melted in the reactor vessel 720. In thisdrawing, numeral 731 denotes the thus melted Ga and Na. Nitrogen isdissolved in the melted Ga and Na, thus leading to the generation of GaNand the growth of crystals.

Another manufacturing apparatus also has been proposed, including twopressure regulators, one of which supplies gas to a reactor vessel andthe other supplies gas to a pressure-resistant vessel, thus allowing gassystems to be controlled independently between in the reactor vessel andin the pressure-resistant vessel provided outside of the reactor vessel(for example, see Patent document 4).

-   Patent document 1: JP 2002-293696 A-   Patent document 2: JP 2001-102316 A-   Patent document 3: JP 2002-68897 A-   Patent document 4: JP 2001-58900 A

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

The liquid phase growth method has the advantages of simplemanufacturing process and the capability of increasing crystals obtainedin size. However, the quality of the crystals obtained is stillinsufficient, and especially in the field of Group III nitrides such asGaN, the improvement of the quality of crystals obtained has beendemanded. Therefore, it is an object of the present invention to providea manufacturing apparatus for Group III nitride crystals and a methodfor manufacturing Group III nitride crystals, by which high qualitycrystals can be manufactured.

Means for Solving Problem

In order to achieve the above-stated object, a crystal manufacturingapparatus of the present invention is for enabling growth of Group IIInitride crystals using a crystal raw material solution containing GroupIII elements, nitrogen and at least one of an alkali metal and analkaline-earth metal. The Group III nitride crystals are grown in anatmosphere of gas containing nitrogen by applying heat and pressurethereto so as to allow the nitrogen and the Group III elements in thecrystal raw material solution to react with each other. The apparatusincludes: a reactor vessel in which the crystal raw material solutioncan be placed; and a gas supplying device for introducing the gascontaining nitrogen into the reactor vessel. The reactor vessel and thegas supplying device are coupled. The reactor vessel has a gas inlet anda gas outlet. Gas containing nitrogen out of the gas containing nitrogenintroduced through the gas inlet that is not used for the reaction isexhausted through the gas outlet.

A crystal manufacturing method of the present invention includes thesteps of preparing a crystal raw material solution containing Group IIIelements, nitrogen and at least one of an alkali metal and analkaline-earth metal in a reactor vessel, applying heat and pressurethereto in an atmosphere of gas containing nitrogen so as to allow thenitrogen and the Group III elements in the crystal raw material solutionto react with each other, whereby Group III nitride crystals are grown.The reactor vessel has a gas inlet and a gas outlet, the reactor vesseland a gas supplying device are coupled, and in the reactor vessel, gascontaining nitrogen out of gas containing nitrogen introduced throughthe gas inlet that is not used for the reaction is exhausted through thegas outlet.

EFFECTS OF THE INVENTION

In order to achieve the above-stated object, the inventors of thepresent invention have conducted a series of investigations. During thecourse of the research, the inventors found that impurities mixed intogas that is to be introduced into a reactor vessel adversely affect thequality of obtained crystals. As a result of additional research, itfurther was found that the mixing of impurities into the gas to beintroduced into the reactor vessel is caused by a pressure-resistantvessel. That is, a conventional apparatus is configured so that gas isintroduced into a pressure-resistant vessel, and such gas is thenintroduced into a reactor vessel. With this configuration, impuritiessuch as water and oxygen, which are attached to a heater, a heatinsulator, an inner wall of the pressure-resistant vessel and the like,are mixed into the site of the crystal growth, which adversely affectsthe quality of crystals obtained. On the other hand, according to theapparatus and the manufacturing method of the present invention, the gascontaining nitrogen is introduced directly to the reactor vessel withoutpassing through the pressure-resistant vessel, thus preventingimpurities attached to the heater, the heat insulator, thepressure-resistant vessel, etc., from mixing into the site of thecrystal growth. As a result, it is possible to improve the quality ofthe crystals obtained. Further, by controlling impurities, gas withreduced impurities can be supplied always from the gas supplying device,and therefore the density of dopants in crystals can be controlledeasily, resulting in improved controllability of the carrier density.

Further, in a conventional apparatus, the following problem occursfrequently: when crystals are grown using alkali metal, the evaporatingalkali metal aggregates at a gas inlet and a pipe connected to the gasinlet, with which the gas inlet and the pipe are clogged, causing afailure in the supply of gas containing nitrogen to a reactor vessel. Inorder to cope with such a problem, the inventors of the presentinvention further conducted investigation. As a result, it was foundthat this was caused by the fact that gas hardly flows in a reactorvessel. That is, in a conventional apparatus, a nitrogen component onlyis supplied through a gas inlet into a reactor vessel that is subjectedto reaction, and gas hardly flows, thus causing aggregation of alkalimetal or the like at the gas inlet and a pipe connected to the gas inletdue to diffusion. Additionally, in some cases, an alkali metal and analkaline-earth metal flow into a pipe connected to a gas inlet and a gassupplying device and chemically attack them, and a dissolved substancegenerated by the chemical-attacking is mixed into the site of thecrystal growth, which adversely affects the quality of crystalsobtained. On the other hand, according to the apparatus and themanufacturing method of the present invention, a reactor vessel usedincludes a gas outlet in addition to a gas inlet, and gas containingnitrogen, introduced through the gas inlet, that is not subjected toreaction in the reactor vessel can be exhausted through the gas outlet,and therefore gas can flow continuously in a fixed direction in thereactor vessel. Thus, the aggregation of an alkali metal, analkaline-earth metal, etc, at the gas inlet, the gas outlet and thepipes connected therewith and the inflow of an alkali metal, analkaline-earth metal, etc, into a gas supplying device through the gasinlet can be prevented. As a result, the quality of crystals obtainedfurther can be improved.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] FIG. 1 is a schematic diagram showing the configuration of oneexample of a crystal manufacturing apparatus of the present invention.

[FIG. 2] FIG. 2 is a schematic diagram showing the configuration ofanother example of a crystal manufacturing apparatus of the presentinvention.

[FIG. 3] FIG. 3 is a schematic diagram showing the configuration ofstill another example of a crystal manufacturing apparatus of thepresent invention.

[FIG. 4] FIG. 4 is a schematic diagram showing a further example of theconfiguration of a crystal manufacturing apparatus of the presentinvention.

[FIG. 5] FIG. 5 is a schematic diagram showing one example of theconfiguration of a reactor vessel of the present invention.

[FIG. 6] FIG. 6 is a schematic diagram showing another example of theconfiguration of a reactor vessel of the present invention.

[FIG. 7] FIG. 7A is a schematic diagram showing still another example ofthe configuration of a reactor vessel of the present invention, andFIGS. 7B and 7C are schematic diagrams showing examples of theconfiguration of a gas inlet and gas outlet in the reactor vessel of thepresent invention.

[FIG. 8] FIG. 8 is a schematic diagram showing a further example of theconfiguration of a reactor vessel of the present invention.

[FIG. 9] FIG. 9 is a schematic diagram showing a still further exampleof the configuration of a reactor vessel of the present invention.

[FIG. 10] FIG. 10 is a schematic diagram showing another example of theconfiguration of a reactor vessel of the present invention.

[FIG. 11] FIG. 11 is a schematic diagram showing still another exampleof the configuration of a reactor vessel of the present invention.

[FIG. 12] FIG. 12 is a schematic diagram showing a further example ofthe configuration of a reactor vessel of the present invention.

[FIG. 13] FIG. 13 is a schematic diagram showing a still further exampleof the configuration of a reactor vessel of the present invention.

[FIG. 14] FIG. 14 is a flowchart showing one example of themanufacturing method of the present invention.

[FIG. 15] FIG. 15 is a flowchart showing another example of themanufacturing method of the present invention.

[FIG. 16] FIG. 16 is a schematic cross-sectional view showing oneexample of a semiconductor element that uses crystals obtained by themanufacturing method of the present invention.

[FIG. 17] FIG. 17 is a schematic diagram showing one example of theconfiguration of a conventional crystal growth apparatus.

DESCRIPTION OF NUMERALS

102, 202, 302, 402, 702 pressure-resistant vessel 103, 203, 303, 403 lidof a pressure-resistant vessel 110, 310, 710, 410 heater 111, 211, 311,411, 711 heat insulator 120, 220, 320, 420, 520, 720 reactor vessel 121,221, 321, 421, 521, 721 lid of a reactor vessel 122, 123, 222, 223, 322,pipe 323, 422, 423, 522, 523 130, 230, 330, 430, 530 crucible 131, 231,331, 431, 531, 731 crystal raw material 140, 141, 240, 241, 340, 341,440, 441 gas open/dose mechanism (valve) 150, 250, 350, 351, 450junction 160, 260, 360, 361, 460 gas flow rate regulator 170, 270, 370,371, 470 pressure regulator 180, 280, 380, 381, 480 gas supplying device212 high-frequency heater 381 second gas supplying device 524 gas inlet525 gas outlet 526 gas exhaustion tube 532 droplets 590 baffle plate 591cooling tube 592 drops guide 593, 724 through hole 90 semiconductorelement 91 substrate 92, 98 contact layer 93, 97 cladding layer 94, 96light-guiding layer 95 multiple quantum well layer 99 insulation film100 p-side electrode 101 n-side electrode

DESCRIPTION OF THE INVENTION

Preferably, the apparatus of the present invention further includes: apressure-resistant vessel; and a heater that applies heat to the reactorvessel. The reactor vessel is stored in the pressure-resistant vessel,and the reactor vessel and the gas supplying device are coupled via thegas inlet. Further, in the apparatus of the present invention,preferably, the gas containing nitrogen supplied from the gas supplyingdevice firstly passes through the gas inlet and is introduced into thereactor vessel, and gas containing nitrogen out of the gas containingnitrogen introduced that is not used for the reaction then can beexhausted through the gas outlet to at least one of an inside of thepressure-resistant vessel and an outside of the pressure-resistantvessel. The number of the gas inlet and the gas outlet is not limitedespecially, and they may be one or plural. Herein, in the apparatus andthe manufacturing method of the present invention, the reactor vessel isnot limited especially, as long as it includes holes capable of lettinggas containing nitrogen in and out of the reactor vessel as the gasinlet and the gas outlet. For instance, pipes or the like may beconnected to the gas inlet and the gas outlet. As specific examples ofthe gas inlet, the configuration with a hole formed in a reactor vesselas a gas inlet and the configuration with a pipe or the like connectedto the hole are included, for example. As specific examples of the gasoutlet, the configuration with a hole formed in a reactor vessel as agas outlet, the configuration with a pipe or the like connected to thehole and the configuration with a gas exhaustion tube, described later,connected to the hole are included.

In the apparatus of the present invention, the gas inlet and the gasoutlet preferably have inner diameters of 10 mm or less, more preferably5 mm or less and still more preferably 0.5 mm to 2 mm. With theabove-stated range, the diffusion of the evaporating alkali metal,alkaline-earth metal, etc, to the gas inlet, the aggregation at the gasinlet, the gas outlet and the pipes connected thereto, and the inflow ofimpurity gas (e.g., water and oxygen) from the heater or the like in thepressure-resistant vessel to the reactor vessel through the gas outletfurther can be suppressed. The ratio between the inner diameter (A) ofthe gas inlet and the inner diameter (B) of the gas outlet (A:B)preferably is 1:2 to 2:1, for example. For instance, in the case wherethe inner diameter of the gas outlet is made smaller with respect to theinner diameter of the gas inlet, the inflow of impurity gas from theoutside of the reactor vessel through the gas inlet further can bereduced. On the other hand, in the case where the inner diameter of thegas outlet is made larger with respect to the inner diameter of the gasinlet, the back-flow of the alkali metal, the alkaline-earth metal,etc., to the gas supplying device through the gas inlet further can beprevented.

In the apparatus of the present invention, a flow velocity of the gascontaining nitrogen at least one of the gas inlet and the gas outlet ofthe reactor vessel preferably is 1 cm/sec to 500 cm/sec, more preferably1 cm/sec to 50 cm/sec and still more preferably 2 cm/sec to 10 cm/sec.More preferably, the flow velocity at both of the gas inlet and the gasoutlet of the reactor vessel is within the above-stated range. With theabove-stated range, the diffusion of the evaporating alkali metal,alkaline-earth metal, etc, to the gas inlet, the aggregation at the gasinlet, the gas outlet and the pipes connected thereto, and the inflow ofimpurity gas (e.g., water and oxygen) from the heater or the like in thepressure-resistant vessel to the reactor vessel through the gas outletfurther can be suppressed. In addition, an increase in evaporation ofthe alkali metal, the alkaline-earth metal, etc., from the crystal rawmaterial solution due to the gas flow can be suppressed. Thus, excellentquality crystals can be obtained with a better reproducibility. Herein,the above-stated flow velocity is a value at an ambient pressure and anambient temperature in the reactor vessel.

Preferably, the apparatus of the present invention further includes acooling tube and a gas exhaustion tube. The gas exhaustion tube isplaced at the gas outlet, and the cooling tube is placed closer to or incontact with the perimeter of the gas exhaustion tube. In this way, byplacing the cooling tube for the gas exhaustion tube and cooling the gasexhausting tube, the vapor such as the alkali metal, the alkaline-earthmetal, etc, can be cooled in the vicinity of the gas outlet to beliquefied (to be droplets), which can be reused as a crystal rawmaterial solution. The gas exhaustion tube may penetrate through the gasoutlet so that one end of the gas exhaustion tube is placed in thereactor vessel, or may be placed outside the reactor vessel via the gasoutlet. The shape of the gas exhaustion tube is not limited especially,and for example, a cylindrical shape, a funnel shape or the like ispossible. For instance, the funnel shape can prevent the clogging of theliquefied alkali metal, the alkaline-earth metals, etc., in the gasexhaustion tube and further can reduce the evaporation of the alkalimetal, the alkaline-earth metal, etc. In this case, the inner diameterof the gas outlet is 3 mm to 50 mm, for example, and preferably 5 mm to20 mm. The internal structure of the gas exhaustion tube, which is not alimiting example, preferably includes funnel structures stacked as amultistage in which adjacent funnel structures have centers displacedfrom each other, so that gas can pass therethrough in a meanderingmanner. The above-stated cooling tube is not limited especially, and acooling tube with an inner diameter of 1 mm to 5 mm, for example, ispreferable because the inside of the reactor vessel can be cooled morelocally. As a coolant flowing through the cooling tube, nitrogen gas andan inert gas (e.g., argon, helium) at a room temperature are available,for example, which are not limiting examples. In this way, by using gasas the coolant, even when the cooling tube is broken partially, thecoolant will not react with the component of the crystal raw materialsolution rapidly.

Preferably, the apparatus of the present invention further includes adrops guide. One end of the drops guide is placed at the gas exhaustiontube, and the other end is placed in the crystal raw material solutionor in the vicinity of a liquid surface of the crystal raw materialsolution. The materials of the gas exhaustion tube and the drops guideare not limited especially, and a material that is less reactive withGroup III elements, alkali metals and alkaline-earth metals, such asalumina, single crystal sapphire, boron nitride (BN), tungsten,tantalum, Y₂O₃, CaO or MgO, can be used.

Preferably, the apparatus of the present invention further includes arecovery device instead of the gas exhaustion tube or in addition to thegas exhaustion tube. The recovery device is connected to the pressureregulator, and the recovery device allows the recovery of the alkalimetal and the alkaline-earth metal evaporating from the crystal rawmaterial solution. Further, the recovery device may allow the recoveryof Group III element, etc., evaporating from the crystal raw materialsolution. This configuration can prevent the evaporating alkali metal,alkaline-earth metal, etc., from being emitted to the air outside theapparatus. The recovery method by the recovery device of an alkali metaland an alkaline-earth metal having a high vapor pressure mainly is notlimited especially, and a method of absorbing them with a porous membersuch as porous ceramic and porous metal is available. Alternatively, inthe recovery device, the vapor such as the alkali metal and thealkaline-earth metal may be allowed to react with oxygen and to beabsorbed into water for recovery, followed by a neutralization process.In general, the contamination by even slight amount of alkali metals,alkaline-earth metals and the like is unfavorable for a semiconductormanufacturing process. The above-stated recovery device can prevent thecontamination by the alkali metals or the alkaline-earth metals as maincomponents of the evaporating substance, even when the present apparatusis installed closer to other semiconductor manufacturing apparatuses.

Preferably, in the apparatus of the present invention, an extra lengthportion is provided to at least one of the gas inlet and the gas outlet.The shape of the extra length portion is not limited especially, and theshape like a coil-form or a waveform is preferable. With thisconfiguration, the alkali metal, the alkaline-earth metal, etc.,evaporating from the crystal raw material solution collide with the tubewall of the extra length portion, thus making it difficult to diffuse tothe outside and suppressing the emission to the outside of the reactorvessel. Thereby, the emission of the vapor such as the alkali metal, thealkaline-earth metal, etc., to the outside of the reactor vessel can besuppressed, thus preventing corrosion of the heater or the like.Further, the diffusion of the evaporating alkali metal, alkaline-earthmetal, etc, to the gas inlet, the aggregation at the gas inlet, the gasoutlet and the pipes connected thereto, and the inflow of impurity gas(e.g., water and oxygen) from the heater or the like in thepressure-resistant vessel to the reactor vessel through the gas outletfurther can be suppressed. Since the extra length portion can preventthe coagulation of the crystal raw material inside the extra lengthportion, the extra portion preferably is formed close to the heater whenthe reactor vessel is placed in the pressure-resistant vessel. Thelength of the extra length portion is not limited especially, and 5 mmor more is preferable, 20 mm or more is more preferable and 100 mm ormore is still more preferable. The range of 50 mm to 500 mm isparticularly preferable. By increasing the length of the extra lengthportion, the diffusion of the alkali metal, the alkaline-earth metal,etc., to the outside of the reactor vessel can be minimized.

In the apparatus of the present invention, preferably, in the reactorvessel, concentration gradient can be formed for the alkali metal andthe alkaline-earth metal evaporating from the crystal raw materialsolution. In this way, by using the reactor vessel in whichconcentration gradient can be formed for the alkali metal and thealkaline-earth metal evaporating from the crystal raw material solution,the evaporation of the alkali metal, the alkaline-earth metal, etc.,from the crystal raw material solution can be suppressed, and theclogging at the gas outlet by the attachment of the evaporating alkalimetal, the alkaline-earth metal, etc., thereto can be suppressed.

In the apparatus of the present invention, as the reactor vessel capableof forming the concentration gradient, a reactor vessel with a gasoutlet formed close to a gas inlet and a reactor vessel having a baffleplate with a through hole formed therein are available, for example. Inthe case where the gas outlet is formed close to the gas inlet, sincegas containing nitrogen is supplied always in the vicinity of the gasinlet, there is a tendency of decreasing the concentration of the alkalimetal, the alkaline-metal, etc., there. As a result, the vicinity of thegas inlet has a low concentration of the alkali metal, thealkaline-earth metal, etc., inside the reactor vessel. For instance, inthe case where the apparatus includes one gas inlet and a plurality ofgas outlets, the gas outlets preferably are formed adjacent to the gasinlet so as to surround the gas inlet. Herein, even when the gas outletis formed close to the gas inlet, since the gas containing nitrogen issupplied excessively relative to an amount required for the crystalgrowth, there is no problem occurring for the crystal growth. On theother hand, by providing a baffle plate, the concentration of the alkalimetal, the alkaline-earth metal, etc., can be made lower at a portionaround the gas outlet than at a portion close to a liquid surface of thecrystal raw material solution. That is, by providing the baffle plate,the evaporation of the alkali metal, the alkaline-earth metal, etc.,from the crystal raw material solution further can be suppressed, sothat the emission of the vapor such as the alkali metal, thealkaline-earth metal, etc., to the outside of the reactor vessel can bereduced.

In the apparatus of the present invention, preferably, the baffle plateis placed in the reactor vessel closer to a liquid surface of thecrystal raw material solution than the gas inlet and the gas outlet. Thenumber of the baffle plate is not limited especially, and it may be oneor plural. In the case where a crucible is placed in the reactor vessel,the baffle plate may be a lid of the crucible. The position of thethrough hole of the baffle plate is not limited especially, andpreferably the through hole is formed so that the gas inlet and thethrough hole of the baffle plate are aligned. For instance, it ispreferable that the inlet is formed at a top wall face portion of thereactor vessel and the through hole is formed directly below. Morepreferably, a pipe is connected to the gas inlet of the reactor vessel,and one end of the pipe is placed in the vicinity of the through hole.With this configuration, the evaporation of the alkali metal, thealkaline-earth metal, etc., from the crystal raw material solutionfurther can be suppressed. The cross-sectional shape of the through holeof the baffle plate is not limited especially, and a taper shape thatwidens gradually toward a side of the gas inlet is available. Thistaper-shaped through hole allows the alkali metal and the alkaline-earthmetal evaporating from the crystal raw material solution to be storedinside, so that the diffusion of the alkali metal and the alkaline-earthmetal can be suppressed. The inner diameter of the through hole is 0.5mm to 20 mm, for example, and preferably 1 mm to 5 mm. With such arange, while sufficient amount of nitrogen required for the crystalgrowth is supplied, and under the condition for further suppressing theevaporation of the alkali metal, the alkaline-earth metal, etc., fromthe crystal raw material, crystals can be grown. The number of thethrough hole is not limited especially, and it may one or plural, andfor example, a plurality of through holes with a relatively small innerdiameter of 0.5 mm to 3 mm, for example, may be formed.

In the apparatus of the present invention, preferably, a junction isplaced at the gas inlet or at both of the gas inlet and the gas outlet,and the reactor vessel is detachable from the inside of thepressure-resistant vessel. Further, in the apparatus of the presentinvention, preferably, a gas open/dose mechanism is placed at least oneof the gas inlet and the gas outlet. With this configuration, thecontact of the crystal raw material or the like with the outside-air canbe prevented, so that the quality of crystals obtained further can beimproved. Such an apparatus can prevent the oxidation of the crystal rawmaterial such as an easily oxidizable alkali metal, so that moreexcellent quality of crystals can be obtained. Herein, it is preferablethat after putting the crystal raw material in the reactor vessel in anatmosphere of an inert gas outside of the pressure-resistant vessel, thereactor vessel is heated to form the crystal raw material solution.Thereby, at least one of the alkali metal and the alkaline-earth metaland the Group III elements can be made an alloy, and as compared withthe case of melting these materials separately, the evaporation of highvapor pressure materials (e.g., the alkali metal and the alkaline-earthmetal) can be suppressed. Note here that the inert gas refers to a raregas such as helium gas or argon gas or nitrogen, which do not react withthe crystal raw material at the respective process temperatures.Although nitrogen can be regarded as an inert gas at a low temperature,it does not behave as an inert gas at a crystal growth temperature butbehaves as a reactive gas. It is preferable that the apparatus of thepresent invention further includes a means for performing agitation ofthe crystal raw material solution. The agitation means is not limitedespecially, and a propeller connected to a rotation motor is available,for example. The material of the propeller is not limited especially,and a material that is less reactive with Group III elements, alkalimetals and alkaline-earth metals, such as alumina, single crystalsapphire, boron nitride (BN), tungsten, tantalum, Y₂O₃, CaO or MgO, canbe used. By heating the crystal raw material and concurrently performingagitation, the crystal raw material solution can be made uniformspeedily. The agitation by the propeller is not limited to during thecrystal growth (at a high pressure), but this may be performed at anormal pressure as well (e.g., in a glove box), which is much easierthan performing agitation at a high pressure.

In the apparatus of the present invention, the gas containing nitrogensupplied from the gas supplying device may control ambient pressures ofboth in the reactor vessel and in the pressure-resistant vessel.Preferably, the apparatus of the present invention further includes agas flow rate regulator; and a pressure regulator. The gas containingnitrogen is introduced from the gas supplying device to the reactorvessel via the gas flow rate regulator, the pressure-resistant vesselhas a gas outlet, to which the pressure regulator is connected, and thegas flow rate regulator and the pressure regulator allow ambientpressures of both in the reactor vessel and in the pressure-resistantvessel to be controlled.

In the apparatus of the present invention, the gas supplying device mayinclude a first gas supplying device and a second gas supplying device.The pressure-resistant vessel may have a gas inlet, the first gassupplying device may be connected to the gas inlet of the reactorvessel, the gas outlet of the reactor vessel directly may communicatewith an outside of the pressure-resistant vessel, the second gassupplying device may be connected to the gas inlet of thepressure-resistant vessel, and the first gas supplying device and thesecond gas supplying device may allow ambient pressures in the reactorvessel and in the pressure-resistant vessel to be controlledindependently. The pressure-resistant vessel further may have a gasoutlet. Preferably, the apparatus of the present invention furtherincludes: a first gas flow rate regulator; a second gas flow rateregulator; a first pressure regulator; and a second pressure regulator.Gas containing nitrogen is introduced from the first gas supplyingdevice to the reactor vessel via the first gas flow rate regulator. Thegas outlet of the reactor vessel is connected to the first pressureregulator. Gas is introduced from the second gas supplying device to thepressure-resistant vessel via the second gas flow rate regulator. Thegas outlet of the pressure-resistant vessel is connected to the secondpressure regulator. The first gas flow rate regulator and the firstpressure regulator allow an ambient pressure in the reactor vessel to becontrolled, and the second gas flow rate regulator and the secondpressure regulator allow an ambient pressure in the pressure-resistantvessel to be controlled.

In the apparatus of the present invention, the gas introduced to thepressure-resistant vessel and the gas containing nitrogen introduced tothe reactor vessel may be different or the same. In the case of beingdifferent, the gas may be different in type or the types may be the samebut they are different in purity. For instance, the gas containingnitrogen introduced to the reactor vessel may be nitrogen, and the gasintroduced to the pressure-resistant vessel may be a rare gas or air.Further, a purity of the gas containing nitrogen introduced to thereactor vessel may be 99.9% or more and a purity of the gas introducedto the pressure-resistant vessel may be 99% or less.

In the apparatus of the present invention, the supplying of the gas maybe controlled by the combination of a pair of a gas flow rate regulatorand a pressure regulator. When the temperature in the reactor vessel isincreased from a room temperature to a crystal growth temperature (e.g.,800° C.), the temperature of the gases in the reactor vessel and in thepressure-resistant vessel is increased and the gases expand. Therefore,in the case of a gas flow rate regulator alone or a pressure regulatoralone, it is difficult to keep the amount of the gas supplied constantconsidering the expansion of the gas. Then, by combining a gas flow rateregulator and a pressure regulator, even when the temperature of theheater varies, the supplying amount of the gas to the reactor vessel andthe pressure-resistant vessel can be kept constant and the ambientpressure also can be kept constant. As a result, the evaporation of analkali metal, an alkaline-earth metal, etc., which have a conspicuoustendency to evaporate, can be suppressed in the reactor vessel, and theminimum gas flow can be controlled optimally. As the gas flow rateregulator and the pressure regulator, conventional ones are available.

In the apparatus of the present invention, the heater is not limitedespecially, and there are an induction heating type heater(high-frequency coil), a resistance heating type heater (nichrome,kanthal, SiC, MoSi₂ heater or the like) and the like. Among them, aninduction heating type heater preferably is used, because of reducedamount of impurity gas generated at a high temperature.

Next, as described above, a manufacturing method of the presentinvention includes the steps of: preparing a crystal raw materialsolution containing Group III elements, nitrogen and at least one of analkali metal and an alkaline-earth metal in a reactor vessel, andapplying heat and pressure thereto in an atmosphere of gas containingnitrogen so as to allow the nitrogen and the Group III elements in thecrystal raw material solution to react with each other, whereby GroupIII nitride crystals are grown. The reactor vessel has a gas inlet and agas outlet, the reactor vessel and a gas supplying device are coupled,and in the reactor vessel, gas containing nitrogen out of gas containingnitrogen introduced through the gas inlet that is not used for thereaction is exhausted through the gas outlet. The manufacturing methodof the present invention can be implemented using the manufacturingapparatus of the present invention.

In the manufacturing method of the present invention, preferably, thereactor vessel is stored in a pressure-resistant vessel, the reactorvessel and the gas supplying device are coupled via the gas inlet, andgas containing nitrogen supplied from the gas supplying device firstlyis introduced to the reactor vessel through the gas inlet, and then gascontaining nitrogen out of gas containing nitrogen introduced that isnot used for the reaction is exhausted through the gas outlet to atleast one of an inside of the pressure-resistant vessel and an outsideof the pressure-resistant vessel.

In the manufacturing method of the present invention, preferably, a flowvelocity of the gas containing nitrogen at the gas inlet and the gasoutlet of the reactor vessel is 1 cm/sec to 500 cm/sec, for example.More preferably, this is set at 1 cm/sec to 50 cm/sec, and still morepreferably is at 2 cm/sec to 10 cm/sec. More preferably, the flowvelocity of the gas containing nitrogen at both of the gas inlet and thegas outlet of the reactor vessel is within the above-stated range. Theflow velocity of the gas can be adjusted by the first gas flow rateregulator and the second gas flow rate regulator using the apparatus ofthe present invention having such first gas flow rate regulator andsecond gas flow rate regulator. Herein, the above-stated flow velocityis a value at an ambient pressure and an ambient temperature in thereactor vessel.

In the manufacturing method of the present invention, preferably, in thereactor vessel, a concentration gradient is formed for at least one ofthe alkali metal and the alkaline-earth metal evaporating from thecrystal raw material solution.

In the manufacturing method of the present invention, preferably, ajunction is placed at the gas inlet or at both of the gas inlet and thegas outlet, and the reactor vessel is detachable from the inside of thepressure-resistant vessel. Further, in the manufacturing method of thepresent invention, a gas open/close mechanism is placed at least one ofthe gas inlet and the gas outlet, and the reactor vessel used isdetachable from the inside of the pressure-resistant vessel. Preferably,prior to crystal manufacturing, outside of the pressure-resistantvessel, a crystal raw material is put in the reactor vessel in anatmosphere of an inert gas. The gas open/close mechanism is closed andthe reactor vessel is hermetically sealed, and the reactor vessel isstored in the pressure-resistant vessel. The reactor vessel is connectedto the gas supplying device via the junction, the gas open/closemechanism is opened, and in this state, the gas containing nitrogen isallowed to be introduced to the reactor vessel. Thereby, since thecontact of the crystal raw material or the like with the outside-air canbe prevented, the oxidation of the alkali metal or the like can beprevented, so that more excellent quality crystals can be obtained.Herein, it is preferable that after putting the crystal raw material inthe reactor vessel in an atmosphere of an inert gas outside of thepressure-resistant vessel, the reactor vessel is heated to form thecrystal raw material solution. Thereby, at least one of the alkali metaland the alkaline-earth metal and the Group III elements can be made analloy, and as compared with the case of melting these materialsseparately, the evaporation of high vapor pressure materials (e.g., thealkali metal and the alkaline-earth metal) can be suppressed. Note herethat the inert gas is as described above.

Preferably, the manufacturing method of the present invention furtherincludes the step of performing agitation of the crystal raw materialsolution. The agitation method of the crystal raw material solution isnot limited especially, and the agitation may be performed by utilizingthermal convection generated by heating the bottom of the reactor vesselto a high temperature, or a propeller connected to a rotation motor maybe submerged in the crystal raw material solution and the propeller maybe rotated for agitation. The material of the propeller is as describedabove. By heating the crystal raw material solution and concurrentlyperforming agitation, the crystal raw material solution can be madeuniform speedily. The agitation by the thermal gradient and thepropeller are not limited for during the crystal growth (at a highpressure), but this may be performed at a normal pressure as well (e.g.,in a glove box), which is much easier than performing agitation at ahigh pressure.

Preferably, in the manufacturing method of the present invention, a gasflow rate regulator and a pressure regulator further are provided, andgas containing nitrogen is introduced from the gas supplying device tothe reactor vessel via the gas flow rate regulator, and thepressure-resistant vessel has a gas outlet, to which the pressureregulator is connected. Preferably, the gas flow rate regulator and thepressure regulator allow ambient pressure both in the reactor vessel andin the pressure-resistant vessel to be controlled, and the same gas isintroduced to the pressure-resistant vessel and to the reactor vessel.

Preferably, in the manufacturing method of the present invention, priorto crystal manufacturing, an impurity gas removal treatment is performedfor the reactor vessel and the pressure-resistant vessel. The impuritygas removal treatment is not limited especially, and baling, evacuation,the combination thereof or the like is available for this purpose.

In the apparatus and the manufacturing method of the present invention,a nitrogen source for the nitrogen contained in the crystal raw materialsolution is not limited especially, and gas containing nitrogen, anitrogen compound mixed in a raw material solution or the like isavailable for this purpose. As the nitrogen compound, hydrazine(H₂NNH₂), sodium azide and the like are available for example. As thegas containing nitrogen, nitrogen gas, ammonia gas or a mixed gas ofthese gases is preferable. The gas containing nitrogen may contain aninert gas (e.g., Ar, He and Ne), hydrogen gas and the like. As thenitrogen-containing-gas source, hydrazine may be used. In this case,since hydrazine is split into ammonia and nitrogen at 180° C., the gasobtained by heating hydrazine may be supplied as it is as the gascontaining nitrogen, or one obtained by diluting with a carrier gas suchas nitrogen N₂) gas and the above-stated inert gas may be supplied forexample.

In the apparatus and the manufacturing method of the present invention,preferably, the Group III elements are at least one selected from thegroup consisting of gallium, aluminum and indium, and the crystals areAl_(x)Ga_(y)In_(1-x-y)N, wherein 0≦x≦1, 0≦y≦1, 0≦x+y≦1.

In the apparatus and the manufacturing method of the present invention,the alkali metal includes lithium, sodium, potassium, rubidium andcesium, and the alkaline-earth metal includes calcium, magnesium,beryllium, strontium, barium and the like, for example. They may be usedalone or in combination of two types or more. Herein, in the presentinvention, the alkaline-earth metal includes calcium, magnesium,beryllium, strontium and barium. In the apparatus and the manufacturingmethod of the present invention, the crystal raw material solution maycontain silicon (Si), zinc (Zn), magnesium (Mg) or the like as n-typeand p-type dopants.

A semiconductor element of the present invention contains Group IIInitride crystals manufactured by the manufacturing method of the presentinvention. A semiconductor light-emitting device of the presentinvention contains Group III nitride crystals manufactured by themanufacturing method of the present invention.

The following describes apparatuses and manufacturing methods of thepresent invention more specifically by way of examples. The presentinvention, however, is not limited to the following examples.

EXAMPLE 1

FIG. 1 shows the configuration of one example of an apparatus accordingto the present invention. As illustrated, this apparatus is providedwith a gas supplying device 180, a reactor vessel 120, apressure-resistant vessel 102 and a heater 110. The reactor vessel 120is stored in the pressure-resistant vessel 102, and a crucible 130 canbe placed in the reactor vessel 120. A lid 103 is placed at the top ofthe pressure-resistant vessel 102 so as to enable hermetic sealing ofthe pressure-resistant vessel 102. A heat insulator 111 is placed closerto an inner wall of the pressure-resistant vessel 102, and the heater110 is placed in a space surrounded by this heat insulator 111. Thereactor vessel 120 is placed so as to be surrounded by this heater 110.The reactor vessel 120 can be closed at the top with a lid 121. A pipe122 is connected to the gas supplying device 180, and a gas flow rateregulator 160, a junction 150 and a gas open/close mechanism (valve) 140are placed along the pipe 122. The leading edge of the pipe 122 isconnected to a gas inlet formed at the lid 121 of the reactor vessel120. Through a gas outlet formed at another part of the lid 121, one endof the other pipe 123 is connected, and a gas open/close mechanism(valve) 141 is placed along this pipe 123. The other end of the pipe 123is placed inside the pressure-resistant vessel 102. In this example, theconfiguration including the gas inlet and the pipe 122 connected to thegas inlet is a gas inlet, and the configuration including the gas outletand the pipe 122 connected to the gas outlet is a gas outlet. Anauxiliary heater or the like may be placed along the pipe 123 connectedto the gas outlet, the gas open/close mechanism 141 placed along thepipe 123 and the like so that the auxiliary heater heats the pipe 123and the like to suppress further the aggregation of an alkali metal, analkaline-earth metals, etc., in the vicinity of the gas outlet. Herein,the crucible 130 used in the present invention is not limitedespecially, and a crucible is made of a material that is less reactivewith Group III elements, alkali metals and alkaline-earth metals, suchas alumina, single crystal sapphire, boron nitride (3N), tungsten,tantalum, Y₂O₃, CaO or MgO. The crucible 130 is not essential to thepresent invention, and a raw material of the crystals may be chargedinto the reactor vessel 120 so as to allow the crystal growth therein.In the case of using the crucible, a lid with micropores for letting gastherein may be placed on the crucible in order to suppress the diffusionof an alkali metal, an alkaline-earth metal, etc., evaporating from thecrystal raw material solution.

FIG. 5 shows one example of the configuration of the reactor vessel usedin the apparatus of the present invention. In FIG. 1, the lengths(heights) of the pipes 122 and 123 connected to the gas inlet and thegas outlet, respectively, are equal to each other. However, as shown inFIG. 5, the pipe connected to the gas outlet may be shorter (lower) thanthe pipe connected to the gas inlet. With this configuration, the pipeconnected to the gas outlet can be brought closer to the heater so thatan alkali metal, an alkaline-earth metal, etc., evaporating from thecrystal raw material solution can flow therethrough easily, thuspreventing the aggregation of the crystal raw material (especially, analkali metal and an alkaline-earth metal) in the pipe connected to thegas outlet. FIG. 6 is another example of the configuration of thereactor vessel used in the apparatus of the present invention. Asillustrated, extra length portions may be provided in the pipesconnected to the gas inlet and the gas outlet. The shape, the length andthe like of the extra length portions are as described above. The shapeof these reactor vessels also applies to the following examples.

The manufacturing method of Group III nitride crystals using theapparatus illustrated in FIG. 1 is described below, based on theflowchart of FIG. 14. This exemplary manufacturing method includes thefollowing six steps:

-   (1-1) Removal of impurities (this step is optional)-   (1-2) Charge of crystal raw material-   (1-3) Hermetically sealing of reactor vessel-   (1-4) Placement of reactor vessel in pressure-resistant vessel and    connection with gas systems (gas inlet side)-   (1-5) Control of pressure applied and control of gas flow-   (1-6) Crystal growth

The following describes these steps more specifically.

(1-1) Removal of Impurities:

As stated above, this step is optional. However, it is preferable toremove impurities from the reactor vessel 120, the crucible 130 or thelike by prebaking, evacuation or the like. Herein, instead of using thecrucible 130, a crystal raw material 131 may be charged in the reactorvessel 120. The removal of impurities by prebaking or the likepreferably is performed prior to the charge of the crystal raw material131 in the reactor vessel 120 or the like.

(1-2) Charge of Crystal Raw Material:

Next, the crystal raw material 131 is charged in the reactor vessel 120or the crucible 130. More specifically, desired amounts of Group IIIelements as the crystal raw material and at least one of an alkali metaland an alkaline-earth metal are weighed, which are then placed in thereactor vessel 120 or the crucible 130. Since the above-stated alkalimetal and alkaline-earth metal react with oxygen and water in the air,the disposition preferably is performed in a glove box in which theinside is substituted with an inert gas (rare gas such as helium gas andargon gas, or nitrogen gas, etc.). Then, the reactor vessel 120 or thecrucible 130 is heated, so as to form a melt containing the above-statedGroup III elements and at least one of the alkali metal and thealkaline-earth metal. At this time, it is preferable to performagitation of the melt. The agitation method of the melt is as describedabove. The agitation of the melt may be performed in a glove box orperformed in the pressure-resistant vessel after the hermeticallysealing of the reactor vessel and the placement of the reactor vessel inthe pressure-resistant vessel, which will be described later. However,various steps of the agitation operation in the glove box (normalpressure) are much easier than in the pressure-resistant vessel (underhigh pressure). Further, as required, seed crystals may be provided atthe same time in the reactor vessel 120 or the crucible 130. A Group IIInitride crystal thin film by vapor phase growth may be used for exampleas the seed crystals. It is preferable that the seed crystals areimmersed in the melt after the agitation of the melt. For instance, theseed crystals may be placed while tilting the reactor vessel 120 or thecrucible 130 so that the seed crystals are not immersed in the melt,whereby the seed crystals will not be immersed in the melt until theagitation of the melt is completed.

(1-3) Hermetically Sealing of Reactor Vessel:

The reactor vessel 120 is covered with the lid 121. At this time, asrequired, a screw or a gasket may be used. Further, the above-stated twogas open/close mechanisms (valves 140, 141) are closed in a glove box(e.g., dew point inside the glove box: −80° C. or less), whereby thereactor vessel 120 becomes a hermetically sealed state.

(1-4) Placement of Reactor Vessel in Pressure-resistant Vessel andConnection with Gas Systems (Gas Inlet Side):

Next, the reactor vessel 120 is placed in the pressure-resistant vessel102, and the reactor vessel 120 and the gas supplying device 180 areconnected via the junction 150. In this state, the gas open/closemechanism (valve) 140 on the gas inlet side is opened, so as tointroduce gas containing nitrogen into the reactor vessel 120. Then,when the pressure in the reactor vessel 120 is somewhat higher than anormal pressure, the gas open/close mechanism (valve) 141 on the gasoutlet side is opened, thereby substituting the inside of the reactorvessel 120 with the gas containing nitrogen while exhausting the gascontaining nitrogen into the pressure-resistant vessel 102. Then, thegas containing nitrogen filling the pressure-resistant vessel 102 isexhausted to the outside via the pipe connected to the gas outlet. Atthis time, the gas flows through the gas supplying device 180, thereactor vessel 120 and the pressure-resistant vessel 102 in this order,so that impurities in the pressure-resistant vessel 102 such as theinner wall will not get mixed in the reactor vessel 120. Further, thisprevents the outside-air from flowing into the reactor vessel 120. Atthe beginning of the introduction of the gas containing nitrogen, thepressure-resistant vessel 102 may be covered with the lid 103. Note herethat prior to this introduction of the gas containing nitrogen or at thetime of the introduction of the gas containing nitrogen, thepressure-resistant vessel 102 may be evacuated using a vacuum pump orthe like. During the evacuation of the pressure-resistant vessel 102,gas may be allowed to flow in the reactor vessel 120 in a degree ofpreventing the backflow of the air. When the air of thepressure-resistant vessel 102 is exhausted sufficiently, theintroduction of the gas containing nitrogen from the gas inlet issuspended, and the pressure-resistant vessel 102 is evacuated to ahigher vacuum. Thereby, impurity gas such as oxygen and water attachedto the heater 110, the heat insulator 111 and the inner wall of thepressure-resistant vessel 102 can be removed.

(1-5) Control of Pressure Applied and Control of Gas Flow

Next, pressure is applied to the inside of the pressure-resistant vessel102 with the gas containing nitrogen. As described above, the gascontaining nitrogen flows through the reactor vessel 120 to thepressure-resistant vessel 102, and therefore the pressure inside thereactor vessel 120 also can be regulated with one pressure regulator 170attached to the pressure-resistant vessel 102. Also, one gas flowregulator 160 will suffice. When a predetermined pressure is achieved,the pressure inside the pressure-resistant vessel 102 is kept constantusing the pressure regulator 170. At this time, since the pressureinside the reactor vessel 120 and the pressure inside thepressure-resistant vessel 102 become substantially equal to each other,the reactor vessel 120 does not require a pressure-resistant property.Thus, there is no need to use a reactor vessel made of an expensivepressure-resistant material, and generally available SUS, alumina andthe like, which are at a low cost, can be used. The pressure in thereactor vessel and the pressure-resistant vessel is in the range of 2atm to 100 atm (2×1.01325×10⁵ Pa to 100×1.01325×10⁵ Pa) for example,preferably in the range of 5 atm to 80 atm (5×1.01325×10⁵ Pa to80×1.01325×10⁵ Pa), and more preferably in the range of 10 atm to 60 atm(10×1.01325×10⁵ Pa to 60×1.01325×10⁵ Pa).

(1-6) Crystal Growth

Next, the reactor vessel 120 is heated to a desired temperature (growthtemperature) by the heater 110, whereby a crystal raw material solutionis formed in the reactor vessel 120. The growth temperature for exampleis in the range of 600° C. to 1,100° C., preferably in the range of 700°C. to 1,000° C. and more preferably in the range of 800° C. to 950° C.Herein, the gas containing nitrogen does not flow by way of thepressure-resistant vessel 102 but is introduced directly to the reactorvessel 120. Therefore, the influence of contamination by the impuritygas generated from the heater 110 and the heat insulator 111 inside thepressure-resistant vessel 102 can be eliminated. Further, the regulationof the flow rate of the gas containing nitrogen by the gas flowregulator 160 prevents the impurity gas from flowing (back-flow) intothe reactor vessel 120. The flow rate of the gas containing nitrogen isfor example in the range of 10 mL/min. to 1,000 mL/min. in terms of 1atm (1×1.01325×10⁵ Pa) (standard state), preferably in the range of 20mL/min. to 300 mL/min. and more preferably in the range of 50 mL/min. to200 mL/min.

With this process, Group III nitride crystals with a diameter of 1 inchto 2 inch (2.54 cm to 5.08 cm) and a thickness of 0.5 mm to 2 mm, forexample, can be grown with good reproducibility and high quality.

EXAMPLE 2

Next, another example of the configuration of an apparatus of thepresent invention is shown in FIG. 4. As illustrated in this drawing,this apparatus has the same configuration as that of the apparatus shownin FIG. 1 except that a recovery device 490 is connected to a pressureregulator 470. The manufacturing method using this apparatus also is thesame as in the above. In this example, since the recovery device isprovided, emission of an alkali metal, an alkaline-earth metal, etc.,evaporating from the crystal raw-material solution to the air outside ofthe apparatus can be prevented. In FIG. 4, numeral 480 denotes a gassupplying device, 460 denotes a gas flow rate regulator, 450 denotes ajunction, 440 and 441 denote gas open/close mechanisms (valves), 402denotes a pressure-resistant vessel, 403 denotes a lid of thepressure-resistant vessel 402, 420 denotes a reactor vessel, 421 denotesa lid of the reactor vessel 420, 430 denotes a crucible, 410 denotes aheater and 411 denotes a heat insulator.

EXAMPLE 3

Next, still another example of the configuration of an apparatus of thepresent invention is shown in FIG. 2. The apparatus of this example hasthe same configuration as that of the apparatus shown in FIG. 1 exceptthat a high-frequency heater is used as the heater and the arrangementof the heat insulator is changed correspondingly in the above-statedapparatus of Example 1. The manufacturing method using this apparatusalso is the same as in the above. As shown in FIG. 2, in this apparatus,a heat insulator 211 is placed around a reactor vessel 220, which issurrounded by a high-frequency heater 212. Since the high-frequencyheater 212 is used, a ceramic material such as alumina may be used forthe reactor vessel 220 and a conductive metal such as tungsten ortantalum may be used as a crucible 230, whereby heat can be applied toportions to be heated effectively. Further, according to this example,since heat is applied to the crucible 230 and a crystal raw material 231only, the heat insulator can be made thinner. Therefore, impurity gasfrom the high-frequency heater 212 and the heat insulator 211 can beminimized, and as compared with Example 1, higher purity crystals can begrown. In FIG. 2, numeral 280 denotes a gas supplying device, 260denotes a gas flow rate regulator, 270 denotes a pressure regulator, 250denotes a junction, 240 and 241 denote gas open/close mechanisms(valves), 202 denotes a pressure-resistant vessel, 203 denotes a lid ofthe pressure-resistant vessel 202 and 221 denotes a lid of the reactorvessel 220. In this example also, a recovery device may be connected tothe pressure regulator 270 as shown in Example 2.

EXAMPLE 4

Next, a further example of the configuration of an apparatus of thepresent invention is shown in FIG. 3. The apparatus of this example isprovided with a second gas supplying device 381, a second gas flow rateregulator 361, a second pressure regulator 371 and a junction 351 inaddition to the apparatus shown in FIG. 1. This apparatus is differentfrom the apparatus shown in FIG. 1 in the following configuration. Apipe 323 connected to a gas outlet formed at a lid 321 of a reactorvessel 320 is connected to a first pressure regulator 370 via thejunction 351, so as to communicate directly with the outside of thepressure-resistant vessel 302. The pressure-resistant vessel 302 has agas inlet and a gas outlet, and the second gas supplying device 381 isconnected to the gas inlet of the pressure-resistant vessel 302 via thesecond gas flow rate regulator 361. The gas outlet of thepressure-resistant vessel 302 is connected to the second pressureregulator 371. Note here that in this example the provision of the gasoutlet at the pressure-resistant vessel is optional, and theconfiguration without the gas outlet and the second pressure regulator371 shown in FIG. 3 also is possible. In this case, a pressure regulatorwith a leak function can be used as the second gas flow rate regulator361. In this example, the recovery device shown in Example 2 may beconnected to the first pressure regulator 370. In FIG. 3, numeral 380denotes a first gas supplying device, 360 denotes a first gas flow rateregulator, 350 denotes a junction, 340 and 341 denote gas open/closemechanisms (valves), 303 denotes a lid of the pressure-resistant vessel302, 330 denotes a crucible, 310 denotes a heater and 311 denotes a heatinsulator. This example allows pressure to be controlled independentlybetween the reactor vessel 320 and the pressure-resistant vessel 302.Thus, during the placement of the reactor vessel 320 into thepressure-resistant vessel 302 and during the crystal growth, anoperation for the growth can be conducted while keeping the inside ofthe reactor vessel 320 as a gas system completely separated from thepressure-resistant vessel 302.

The manufacturing of crystals using this apparatus is described below,based on the flowchart of FIG. 15. This exemplary manufacturing methodincludes the following six steps:

-   (3-1) Removal of impurities (this step is optional)-   (3-2) Charge of crystal raw material-   (3-3) Hermetically sealing of reactor vessel-   (3-4) Placement of reactor vessel in pressure-resistant vessel and    connection with gas systems (gas inlet side and gas outlet side)-   (3-5) Control of pressure applied to reactor vessel and    pressure-resistant vessel independently and control of gas flow-   (3-6) Crystal growth

Among the above-stated steps, the steps of (3-1) to (3-3) are the sameas the steps (1-1) to (1-3) of Example 1. Therefore, the steps (3-4) to(3-6) are described below.

(3-4) Placement of Reactor Vessel in Pressure-resistant Vessel andConnection with Gas Systems (Gas Inlet Side and Gas Outlet Side)

The reactor vessel 320 is placed in the pressure-resistant vessel 302.The reactor vessel 320 and the first gas supplying device 380 areconnected via the junction 350, and the reactor vessel 320 and the firstpressure regulator 370 are connected via the other junction 351. In thisstate, similarly to Example 1, gas is introduced into the reactor vessel320. Note here that prior to this introduction of the gas or at the timeof the introduction of the gas, the gas open/close mechanism (valve) 340on the gas inlet side and the gas open/close mechanism (valve) 341 onthe gas outlet side are opened so as to evacuate the reactor vesselonce, which is for exhausting impurity gas from pipes.

(3-5) Control of Pressure Applied to Reactor Vessel andPressure-resistant Vessel Independently and Control of Gas Flow

Next, pressure is applied to the inside of the reactor vessel 320 withgas containing nitrogen supplied from the first gas supplying device380, and pressure is applied to the inside of the pressure-resistantvessel 302 with gas supplied from the second gas supplying device 381.The pressure in the reactor vessel 320 is controlled by the combinationof the first gas flow rate regulator 360 and the first pressureregulator 370, and the pressure in the pressure-resistant vessel 302 iscontrolled by the combination of the second gas flow rate regulator 361and the second pressure regulator 371, and they are controlledindependently. At this time, the pressure in the reactor vessel 320 andthe pressure in the pressure-resistant vessel 302 may be equal to ordifferent from each other. If the pressure in the pressure-resistantvessel 302 is higher the pressure in the reactor vessel 320, the sealingproperty of the reactor vessel 320 is improved. If the pressure in thereactor vessel 320 and the pressure in the pressure-resistant vessel 302are controlled to be substantially equal to each other, the reactorvessel 320 does not require a significant pressure-resistant property.The pressure in the reactor vessel 320 and the pressure in thepressure-resistant vessel 302 are similar to Example 1.

(3-6) Crystal Growth

Next, similarly to Example 1, crystals are grown. During the crystalgrowth, a desired flow rate of gas containing nitrogen is allowed toflow continuously in the reactor vessel 320. Thereby, a high purity gascontaining nitrogen can be supplied always to a crystal raw materialwithout influences of impurity gas attached to the wall of the reactorvessel 320 and the like. As a result, a high purity crystal raw materialsolution can be maintained. At this time, as for the gas containingnitrogen, a high purity gas can be used only for the inside of thereactor vessel 320, which can be independent of the purity and types ofthe gas in the pressure-resistant vessel 302. For instance, argon gaswith a purity of 99% or nitrogen gas with a purity of 99%, etc, can beused for the gas introduced into the pressure-resistant vessel 302 fromthe second gas supplying device 381, whereas a high purity gas with apurity of about 99.9% to 99.99999% can be used for the gas containingnitrogen introduced into the reactor vessel 320 from the first gassupplying device 380. In this case, the size of the reactor vessel 320may be somewhat larger than the size of crystals to be grown, which canbe significantly smaller than the pressure-resistant vessel 302, thusleading to the feature of reducing the consumption amount of expensivehigh-purity gas. Further, as the gas introduced into thepressure-resistant vessel 302, gas such as argon may be used, forexample, whereby the reactor vessel 320 even made of a stainless steelvessel at a low cost can be free from rust. Further, in the case wherethe reactor vessel 320 is made of a material resistant to oxidizing evenat a high temperature such as nickel alloy (e.g., Inconel andhastelloy), the gas introduced into the pressure-resistant vessel 302may be the air. In this example, the gas system introduced into thereactor vessel 320 and the gas system introduced into thepressure-resistant vessel 302 should be controlled independentlyconcerning the pressure and the flow rate, and therefore the control ofgas may become complicated to some degree. However, as described above,a high purity gas can be used only for the gas introduced into thereactor vessel 320, thus resulting in the reduction of a running cost ofthe apparatus. Further, in the case where gas containing oxygen (e.g.,the air) is used as the gas in the pressure-resistant vessel, amolybdenum-based heater (MoSi₂ heater or the like), which can be used ata very high temperature even with resistance heating, is available, thusleading to the feature of being advantageous in the crystal growth ofAlN based materials especially.

With these steps, in the case where 99.9% nitrogen gas is used as thegas introduced into the pressure-resistant vessel 302, a stainless steelvessel is used as the reactor vessel 320 and alumina is used as thecrucible 330, Group III nitride crystals with a thickness of about 1 mmcan be grown on a template with a diameter of 1 inch to 2 inch (2.54 cmto 5.08 cm) at a pressure of 40 atm (40×1.03125×10⁵ Pa) in the reactorvessel 302 and the pressure-resistant vessel 302 and a growthtemperature of 800° C. for a growth time of 100 hours, for example.

EXAMPLE 5

FIG. 7A shows another example of the configuration of the reactor vesselused in the apparatus of the present invention. As illustrated in thisdrawing, a reactor vessel 520 can be closed at the top with a lid 521. Acrucible 530 can be placed in the reactor vessel 520 and a crystal rawmaterial solution 531 can be put in the crucible 530. A gas inlet and agas outlet are formed at the lid 521 to be adjacent to each other, towhich a pipe 522 and a pipe 523 are connected, respectively. In thisway, by forming the gas outlet adjacent to the gas inlet, gas can beexhausted from a region having a low concentration of an alkali metal,an alkaline-earth metal, etc., in the reactor vessel, thus furthersuppressing the evaporation of the alkali metal, the alkaline-earthmetal, etc., from the crystal raw material solution. FIGS. 7B and C arecross-sectional views of the pipes in the vicinity of the reactorvessel, which are examples of the configuration of the gas inlet and thegas outlet. FIG. 7B shows one example of the configuration in which agas inlet 524 and a gas outlet 525 are formed adjacent to each other,and FIG. 7C shows one example of the configuration in which a pluralityof gas outlets 525 are formed adjacent to the perimeter of the gas inlet524.

FIG. 8 shows still another example of the configuration of the reactorvessel used in the apparatus of the present invention. In this drawing,the same numerals are assigned to the same elements as in FIG. 7A. Asshown in this drawing, a baffle plate 590 is placed inside a reactorvessel 520 and over a crucible 530. A through hole 593 is formed at thecenter portion of the baffle plate 590. A gas inlet and a gas outlet areformed to face each other in a lid 521, and pipes 522 and 523 areconnected to the gas inlet and the gas outlet, respectively. Thisconfiguration further can suppress the evaporation of an alkali metal,an alkaline-earth metal, etc., from the crystal raw material solution.As a result, the emission of vapor of the alkali metal, thealkaline-earth metal, etc., to the outside of the reactor vessel can bereduced. Although the baffle plate is placed in the reactor vessel 520in this example, this is not a limiting example, and the baffle platemay be placed in the lid 521. Further, as described above, instead of orin addition to the baffle plate, a lid with micropores for letting gaspass through may be placed over the crucible.

FIGS. 9 and 10 show further examples of the configuration of the reactorvessel used in the apparatus of the present invention. In thesedrawings, the same numerals are assigned to the same elements as in FIG.8. As shown in FIG. 9, a gas inlet and a gas outlet are formed at thetop wall face of a lid 521, to which pipes 522 and 523 are connectedrespectively. One end of the pipe 522 connected to the gas inlet isplaced closer to a through hole 593 formed at the center portion of abaffle plate 590. This configuration further can suppress theevaporation of an alkali metal, an alkaline-earth metals, etc., from thecrystal raw material solution. The shape of the through hole 593 in thebaffle plate 590 is not limited especially, and for example, as shown inFIG. 10, a taper shape that widens gradually toward the gas inlet sideis possible.

In the case where the reactor vessel shown in FIG. 8 is used, GaNcrystals can be manufactured as in the following, for example. Firstly,a rector vessel with a gas inlet and a gas outlet whose inner diametersare 2 mmφ is prepared. Then, metals of Na and Ga (total weight: 28 g)and GaN (2 inch, thickness of seed layer: 5 μm), which is grown as seedcrystals by vapor phase growth on a sapphire substrate, are placed inthe crucible 530. The crucible 530 is placed in the reactor vessel 520,to which heat is applied by the heater and pressure is applied, so as togrow crystals under the following conditions, for example:

-   -   flow rate of gas containing nitrogen (standard state): 100        mL/min.    -   crystal growth temperature: 850° C.    -   pressure during crystal growth: 40 atm (40×1.01325×10⁵ Pa)    -   gas flow velocity at the gas inlet and the gas outlet (850° C.        and 40 atm (40×1.01325×10⁵ Pa)): 5 cm/sec.

As a result of the crystal growth for 96 hours, GaN crystals with athickness of 1 mm to 3 mm and with a low degree of dislocation can beobtained, and the evaporation of an alkali metal, an alkaline-earthmetal, etc., can be suppressed within the range of about 1 to 10%.Further, according to the apparatus of the present invention, there isno aggregation of the alkali metal, the alkaline-earth metal, etc., atthe gas inlet and the gas outlet and in the pipes connected thereto, andimpurity gas (e.g., oxygen and water) from the heater and the heatinsulator outside of the reactor vessel does not enter into the reactorvessel, thus allowing high quality crystals to be grown.

EXAMPLE 6

FIGS. 11 to 13 show still further examples of the configuration of thereactor vessel used in the apparatus of the present invention. In thesedrawings, the same numerals are assigned to the same elements. As shownin FIG. 11, a reactor vessel 520 can be closed at the top with a lid521. A crucible 530 can be placed in the reactor vessel 520 and acrystal raw material solution 531 can be put in the crucible 530. A gasinlet and a gas outlet are formed in the lid 521 so as to face eachother, to which a pipe 522 and a pipe 523 are connected, respectively.The pipe 523 connected to the gas outlet is connected so as to penetratethrough the gas outlet, and one end thereof is placed in the reactorvessel 520. A cooling tube 591 is brought close to or in contact withand is wound around the portion of the pipe 523 placed in the reactorvessel 520, thus cooling the pipe 523. With this configuration, thevapor such as an alkali metal evaporating in the vicinity of the gasoutlet can be cooled to be droplets 532, which then can be recovered(liquefied) and reused as a crystal raw material solution.

In the further example of the configuration of the reactor vessel shownin FIG. 12, a gas outlet is placed at a top wall face of a lid 521, anda pipe (also called gas exhaustion tube) 526 connected to the gas outlethas a funnel shape. This funnel shape of the gas outlet pipe 526 whoseinner diameter is made larger on the reactor vessel side can prevent theclogging of the alkali metal, the alkaline-earth metals, etc., whichevaporate and then are liquefied, in the gas exhaustion tube and furthercan reduce the evaporation of the alkali metal, the alkaline-earthmetal, etc.

In the further example of the configuration of the reactor vessel shownin FIG. 13, a drops guide 592 further is provided, and one end of thedrops guide 592 is placed in a gas exhaustion tube 526 and the other endis placed in the crystal raw material solution 531 or closer to theliquid surface. The internal structure of the gas exhaustion tubeincludes funnel structures stacked as a multistage in which the funnelstructures have centers displaced from each other. Similarly to FIG. 12,a cooling tube is placed closer to or in contact with the gas exhaustiontube 526 (not illustrated). Such a drops guide allows the liquefiedalkali metal, alkaline-earth metal, etc., to be returned quietly withoutdisturbing the crystal raw material solution in the crucible.

The apparatus of the present invention is not limited to these examples,and for example, the configuration provided with both of the baffleplate and the gas exhaustion tube also is possible.

EXAMPLE 7

The following describes a semiconductor element of the presentinvention. The semiconductor element includes a substrate containingGroup III nitride crystals obtained by the manufacturing method usingthe apparatus of the present invention. FIG. 16 shows an exemplaryconfiguration of a semiconductor element 90 of the present invention.

First, on a substrate 91 including Group III nitride crystals obtainedby the manufacturing method of the present invention is formed a contactlayer 92 of n-type GaN doped with Si to have a carrier density of 5×10¹⁸or lower. In GaN-based crystals (crystals containing Ga and N), when Siis added thereto as an impurity, holes present in Ga increase in number.Since the holes present in Ga diffuse easily, they adversely affect interms of, for example, lifetime when a device is formed on the contactlayer. Hence, the doping amount may be controlled so that the contactlayer has a carrier density of 5×10¹⁸ or lower.

Next, on the contact layer 92 are formed a cladding layer 93 of n-typeAl_(0.07)Ga_(0.93)N and a light guiding layer 94 of n-type GaN.Subsequently, as an active layer 95 is formed a multiple quantum well(MQW) composed of a well layer (with a thickness of about 3 nm) made ofGa_(0.8)In_(0.2)N and a barrier layer (with a thickness of about 6 nm)made of GaN. Thereafter, on the active layer 95 are formed sequentiallya light guiding layer 96 of p-type GaN, a cladding layer 97 of p-typeAl_(0.07)Ga_(0.93)N, and a contact layer 98 of p-type GaN. These layerscan be formed by well-known methods. The semiconductor element 90 is asemiconductor light-emitting device of a double-hetero junction type.The energy gap of the well layer containing indium in the MQW activelayer 95 is smaller than those of the n-type and p-type cladding layerscontaining aluminum. On the other hand, the highest optical refractiveindex is obtained in the well layer of the active layer 95, followed bythe light guiding layers and the cladding layers having opticalrefractive indices decreasing in this order.

On the contact layer 98 is formed an insulation film 99 forming acurrent injection region having a width of about 2 μm. A ridge part toserve as a current constriction part is formed in the p-type contactlayer 98 and in the upper portion of the p-type cladding layer 97. Onthe upper side of the p-type contact layer 98 is formed a p-sideelectrode 100 that is in ohmic contact with the contact layer 98. Thep-side electrode 100 may be formed of a lamination of nickel (Ni) andgold (Au). On the n-type contact layer 92 is formed an n-side electrode101 that is in ohmic contact with the contact layer 92. The n-sideelectrode 101 may be formed of a lamination of titanium (Ti) andaluminum (Al).

The semiconductor light-emitting device produced by the method describedabove was subjected to a device evaluation. When a predetermined forwardvoltage is applied between the p-side electrode and the n-side electrodeof the obtained semiconductor light-emitting device, positive holes andelectrons are injected into the MQW active layer from the p-sideelectrode and the n-side electrode, respectively, to be recombined witheach other in the MQW active layer and thereby an optical gain isproduced. Consequently, it is possible to generate laser oscillationwith an emission wavelength of 404 nm.

In the semiconductor light-emitting device of the present example, asubstrate with a low dislocation density, which can be obtained byliquid phase growth using an alkali metal based flux, is used as itssubstrate. Accordingly, the semiconductor light-emitting device has alower threshold, improved luminous efficiency, and improved reliabilityas compared to conventional one produced on a GaN substrate with a highdislocation density.

Incidentally, GaN crystals may be obtained by the manufacturing methodof the present invention, in which a substrate obtained by growing GroupIII nitride crystal thin film on a sapphire substrate by vapor phasegrowth is used as seed crystals. In such a case, the sapphire portionother the GaN crystals may be removed by grinding or the like, so as toproduce a GaN substrate, on which a device can be manufactured.

As stated above, Group III nitride crystals obtained by themanufacturing method using the apparatus of the present invention isused as a substrate, and Group III nitride crystals further areepitaxial-grown on the substrate, whereby a semiconductor deviceprovided with a semiconductor element such as a LD or LED can beobtained. The above description exemplifies GaN as one example of theGroup III nitride crystals obtained by the manufacturing method of thepresent invention. However, the present invention is not limited tothis, and even when other Group III nitride crystals obtained by themanufacturing method using the apparatus of the present invention areused, a semiconductor device provided with a semiconductor element suchas a LD or LED can be obtained. Group III nitride crystals obtained bythe manufacturing method of the present invention has a small defectdensity, thus realizing a light-emitting device having high reliabilityand free from device deterioration even when the optical output power islarge.

The above description exemplifies the semiconductor element as alight-emitting device. However, the present invention is not limited tothis, and an electronic device such as a field effect transistor (FET),for example, can be manufactured using Group III nitride crystalsobtained by the manufacturing method of the present invention.

Industrial Applicability

As described above, according to the present invention, a crystalmanufacturing apparatus for growing high quality Group III nitridecrystals, a manufacturing method of Group III nitride crystals using thesame and a Group III nitride semiconductor element having excellentproperties using the Group III nitride crystals obtained therethroughcan be realized. Further, a GaN single crystal substrate obtained by themanufacturing method and the manufacturing apparatus of the presentinvention has a smaller dislocation density than a substratemanufactured by vapor phase growth (e.g., HVPE) or the like, which issignificantly advantageous in increasing an output power of asemiconductor laser and increasing lifetime thereof.

The invention claimed is:
 1. A crystal manufacturing apparatus thatgrows Group III nitride crystals using a crystal raw material solutioncontaining Group III elements, nitrogen and at least one of an alkalimetal and an alkaline-earth metal, the Group III nitride crystals beinggrown in an atmosphere of gas containing nitrogen by applying heat andpressure thereto so as to allow the nitrogen and the Group III elementsin the crystal raw material solution to react with each other, theapparatus comprising: a reactor vessel having a main body, a lid, a gasinlet and a gas outlet, in which the crystal raw material solution canbe placed; a pressure-resistant vessel having a main body and a lid, inwhich the reactor vessel can be placed; and a gas supplying device forintroducing the gas containing nitrogen into the reactor vessel, whereinthe reactor vessel and the gas supplying device are coupled directly sothat gas is supplied from the gas supplying device to the gas inlet ofthe reactor vessel without being exoosed to the pressure-resistantvessel, and gas containing nitrogen that is not used for the reaction isexhausted through the gas outlet.
 2. The apparatus according to claim 1,further comprising: a pressure-resistant vessel; and a heater thatapplies heat to the reactor vessel, wherein the reactor vessel is storedin the pressure-resistant vessel, and the reactor vessel and the gassupplying device are coupled via the gas inlet.
 3. The apparatusaccording to claim 2, wherein the gas containing nitrogen supplied fromthe gas supplying device firstly passes through the gas inlet and isintroduced into the reactor vessel, and then can be exhausted throughthe gas outlet to at least one of an inside of the pressure-resistantvessel and an outside of the pressure-resistant vessel.
 4. The apparatusaccording to claim 1, wherein the gas inlet and the gas outlet areformed to be adjacent to each other.
 5. The apparatus according to claim1, comprising a plurality of gas outlets, wherein the gas outlets areformed adjacent to the perimeter of the gas inlet.
 6. The apparatusaccording to claim 1, further comprising a baffle plate with a throughhole formed therein, wherein the baffle plate is placed in the reactorvessel closer to a liquid surface of the crystal raw material solutionthan the gas inlet and the gas outlet.
 7. The apparatus according toclaim 6, wherein the gas inlet and the through hole of the baffle plateare aligned.
 8. The apparatus according to claim 7, wherein across-sectional shape of the through hole of the baffle plate is a tapershape that widens gradually toward a side of the gas inlet.
 9. Theapparatus according to claim 1, further comprising: a cooling tube; anda gas exhaustion tube, wherein the gas exhaustion tube is placed at thegas outlet, and the cooling tube is placed close to or in contact withthe perimeter of the gas exhaustion tube.
 10. The apparatus according toclaim 9, wherein the gas outlet is formed at a side wall face of thereactor vessel.
 11. The apparatus according to claim 9, wherein the gasoutlet is formed at a top wall face of the reactor vessel.
 12. Theapparatus according to claim 11, wherein the gas exhaustion tube isplaced outside of the reactor vessel via the gas outlet, and the gasexhaustion tube has a funnel shape.
 13. The apparatus according to claim12, further comprising a drops guide, wherein one end of the drops guideis placed at the gas exhaustion tube, and the other end is placed in thecrystal raw material solution or in the vicinity of a liquid surface ofthe crystal raw material solution, and an internal structure of the gasexhaustion tube includes funnel structures stacked as a multistage, inwhich adjacent funnel structures have centers displaced from each other.14. The apparatus according to claim 2, wherein a junction is placed atthe gas inlet or at both of the gas inlet and the gas outlet, and thereactor vessel is detachable from the inside of the pressure-resistantvessel.
 15. The apparatus according to claim 14, wherein a gasopen/close mechanism is placed at at least one of the gas inlet and thegas outlet.
 16. The apparatus according to claim 1, wherein the gasinlet and the gas outlet have inner diameters of 10 mm or less.
 17. Theapparatus according to claim 1, wherein an extra length portion isprovided to at least one of the gas inlet and the gas outlet.
 18. Theapparatus according to claim 17, wherein a shape of the extra lengthportion is like a coil-form or a waveform.
 19. The apparatus accordingto claim 17, wherein a length of the extra length portion is 5 mm ormore.
 20. The apparatus according to claim 17, wherein a length of theextra length portion is 20 mm or more.
 21. The apparatus according toclaim 17, wherein a length of the extra length portion is 100 mm ormore.
 22. The apparatus according to claim 2, wherein the gas supplyingdevice controls ambient pressures of both in the reactor vessel and inthe pressure-resistant vessel.
 23. The apparatus according to claim 22,further comprising: a gas flow rate regulator; and a pressure regulator,wherein the gas containing nitrogen is introduced from the gas supplyingdevice to the reactor vessel via the gas flow rate regulator, thepressure-resistant vessel has a gas outlet, to which the pressureregulator is connected, and the gas flow rate regulator and the pressureregulator allow ambient pressures in the reactor vessel and in thepressure-resistant vessel to be controlled.
 24. The apparatus accordingto claim 23, further comprising a recovery device, wherein the recoverydevice is connected to the pressure regulator, and the recovery deviceallows recovery of at least one of the alkali metal and thealkaline-earth metal evaporating from the crystal raw material solution.25. The apparatus according to claim 2, wherein the gas supplying devicecomprises a first gas supplying device and a second gas supplyingdevice, the pressure-resistant vessel has a gas inlet, the first gassupplying device is connected to the gas inlet of the reactor vessel,the gas outlet of the reactor vessel directly communicates with anoutside of the pressure-resistant vessel, the second gas supplyingdevice is connected to the gas inlet of the pressure-resistant vessel,and the first gas supplying device and the second gas supplying deviceallow ambient pressures in the reactor vessel and in thepressure-resistant vessel to be controlled independently.
 26. Theapparatus according to claim 25, wherein the pressure-resistant vesselfurther has a gas outlet.
 27. The apparatus according to claim 26,further comprising: a first gas flow rate regulator; a second gas flowrate regulator; a first pressure regulator; and a second pressureregulator, wherein gas containing nitrogen is introduced from the firstgas supplying device to the reactor vessel via the first gas flow rateregulator, the gas outlet of the reactor vessel is connected to thefirst pressure regulator, gas is introduced from the second gassupplying device to the pressure-resistant vessel via the second gasflow rate regulator, the gas outlet of the pressure-resistant vessel isconnected to the second pressure regulator, the first gas flow rateregulator and the first pressure regulator allow an ambient pressure inthe reactor vessel to be controlled, and the second gas flow rateregulator and the second pressure regulator allow an ambient pressure inthe pressure-resistant vessel to be controlled.
 28. The apparatusaccording to claim 1, wherein a flow velocity of the gas containingnitrogen at at least one of the gas inlet and the gas outlet of thereactor vessel is 1 cm/sec to 500 cm/sec.
 29. The apparatus according toclaim 27, wherein the gas containing nitrogen introduced to the reactorvessel and the gas introduced to the pressure-resistant vessel havedifferent purities.
 30. The apparatus according to claim 29, wherein apurity of the gas containing nitrogen introduced to the reactor vesselis 99.9% or more and a purity of the gas introduced to thepressure-resistant vessel is 99% or less.
 31. The apparatus according toclaim 27, wherein the gas containing nitrogen introduced to the reactorvessel and the gas introduced to the pressure-resistant vessel aredifferent in types.
 32. The apparatus according to claim 31, wherein thegas containing nitrogen introduced to the reactor vessel is nitrogen,and the gas introduced to the pressure-resistant vessel is a rare gas.33. The apparatus according to claim 31, wherein the gas containingnitrogen introduced to the reactor vessel is nitrogen, and the gasintroduced to the pressure-resistant vessel is air.
 34. The apparatusaccording to claim 27, further comprising a recovery device, wherein therecovery device is connected to the first pressure regulator, and therecovery device allows recovery of at least one of the alkali metal andthe alkaline-earth metal evaporating from the crystal raw materialsolution.
 35. The apparatus according to claim 2, wherein the heater isan induction heating type heater.
 36. The apparatus according to claim1, wherein the Group III elements are at least one selected from thegroup consisting of gallium, aluminum and indium, and the crystals areAl_(x)Ga_(y)In_(1-x-y)N, wherein 0≦x≦1, 0≦y≦1, 0≦x+y≦1.
 37. Theapparatus according to claim 1, wherein the gas containing nitrogen is anitrogen gas, an ammonia gas or a mixed gas of the nitrogen gas and theammonia gas.
 38. The apparatus according to claim 37, wherein the gascontaining nitrogen further comprises at least one of an inert gas andhydrogen gas.